1. Field of the Invention
The present invention relates generally to an improved process for removing iron from an aqueous acid solution containing iron and copper, and more particularly, but not by way of limitation, to a process for removing iron from an aqueous sulfuric acid leach solution containing copper ions without removing substantial portions of the copper ions from the solution so that the copper ions can be subsequently efficiently recovered in an electrowinning process.
2. Description of the Prior Art
Copper hydrometallurgy has heretofore been utilized, particularly in recent years, for the recovery of copper values from low grade ores. Hydrometallurgy methods of recovering copper from ores generally avoid air pollution problems associated with heretofore used ore roasting processes, i.e., the discharge of sulfur dioxide into the atmosphere. While processes have been developed for recovering sulfur dioxide from the effluent gases produced in ore roasting, such processes generally require elaborate apparatus to carry out.
Heretofore, copper hydrometallury processes have included the steps of contacting ore containing copper with an aqueous sulfuric acid leach solution so that copper contained in the ore is dissolved by the acid. Other metals contained in the ore are also dissolved, particularly iron which is removed from the acid leach solution by precipitation as iron hydroxide. Generally, the iron precipitation is brought about by the addition of calcium carbonate to the acid leach solution. That is, calcium carbonate is added to the acid leach solution to adjust the pH thereof to a value greater than about 2.5 which causes iron contained in the solution to be hydrolyzed and precipitated. The precipitate is separated from the solution and the solution then subjected to an electrowinning process for the recovery of copper. A major drawback to this and other prior art processes is that substantial amounts of copper contained in the acid leach solution are hydrolyzed and precipitated along with iron contained therein, which copper is not recovered.
In order to overcome the loss of copper in the above-described process, the acid leach solution is often subjected to an electrowinning process for the recovery of copper prior to precipitating iron from the solution. However, this technique is also disadvantageous in that iron contained in the acid leach solution interferes with the electrowinning process making it relatively inefficient for copper recovery.
By the present invention an improved process for removing iron from aqueous acid solutions containing copper without removing a major portion of the copper therefrom is provided. The use of the process of the present invention allows the efficient removal of iron from an acid leach solution and the subsequent efficient electrowinning of copper from the solution.